Space Questions: Gravity's Pull, Cosmic Debris & Habitability Zones

Professor Fred Watson: Yeah, good to see you again, Heidi, as always. And, um, yes, this could be the longest goodbye ever. Couldn't it really? It could go on for weeks. It's like when you, uh, are parting ways with someone, you say goodbye and then you realize you're walking the same direction. Professor Fred Watson: Yeah, yeah, exactly. I know. Yeah. I do that all the time. And then I never quite know. It's like, well, do I keep talking to them? Do I say goodbye

again? Do I pretend they're not there? I usually end up commentating and narrating the whole thing to make it more awkward. Um, well, anyways, let's just jump into our questions because you guys have some really fantastic questions, as always, which we appreciate. Our first question of the evening is a written question from John Kerr. And John says, hey, space nutters. This dilemma is driving

me nuts. If the moon's gravitational pull has such an effect on our Ocean's tides, for example, a, uh, 30 centimeter rise in tidal waters twice a day, that's a lift of 300 kg worth of water per meter square. Why doesn't the moon's gravity affect us as drastically as the oceans? I will sleep better once resolved with. Thanks. Oh, so I have so much. I have so much. I feel like I could say about this one too. But please get Fred. Professor Fred Watson: You might give a better answer than me,

Heidi. Um, so it. Yes, well, it does. The moon's gravity does affect us as drastically as the oceans because we go up and down with the oceans. Uh, in fact, the land itself goes up and down slightly. If I remember. It's about a foot or something. Oceans sometimes go, uh, much, much more than that. Um, that 30 centimeter that John mentions. Uh, you know, sometimes it's many, many meters. So what's, um,

happening here? It's. The critical feature of tides is that they are caused because of the difference in the gravitational pull of a body like the moon. And let's just think about the moon and the Earth. Uh, it's a difference between the moon's pull on one side of the earth and the other side of the Earth. So tides are all about the difference in the gravitational pull of an object, uh, across the diameter of another object, a big object, and that's the

Earth. And so, um, the reason why our bodies don't stretch and shrink is that we're only, you know, we're only a couple of meters tall. Uh, actually my son's a two meters tall, but that's quite tall. All right, one and a half meters tall. But we're certainly not, uh, tens of thousands of kilometers, uh, which is what you need for the gravitational effect to be noticeable, um, as it is with the ocean tides. So we don't get stretched and um, shrunk. We would if we were near a black

hole. That's the principle of spaghettification. It's when your feet feel a higher gravitational pull than your head head and you get turned into spaghetti. Uh, that's a uh, tidal effect, uh, an extreme tidal effect. But um, you need something very peculiar like a black hole to notice that. So for, ah, an object like the moon, we simply just go up and down with the oceans. If we're on the ocean, we go up and down with the land if

we're on the land. But we don't get stretched and shrunk because we're too small. I hope he's Jonas. I hope you sleep better after that. Well, maybe I'll scare him because I was gonna say, but it does affect us a little bit. Not like the oceans at all. But the human body is roughly 60% water and every cell in our body is roughly 70 to 80% water. Now what I'm about to say next is not something I'm looking at a science review for. It's

more anecdotal. But, um, nurses will all stay like often say that there is way more um, emergency room activity on a full moon. Police officers will say that people are crazier on a full moon. And there's a lot of lore around women's cycles aligning, ah, with moon cycles. Um, more women go into labor and give birth around the moon cycles. And historically there is a lot of um, I guess stories about personality around moons. You think of werewolf stories. So humans do. We

are affected by the moon to some degree. And that would be an interesting, probably further research. And I'm sure there's whole departments dedicated to the psychobiological effects of humans and the moon. But it is interesting. So no we're not affected like the oceans but there is some, something to that. Professor Fred Watson: Absolutely. Yeah. And you, you, you're quite

right. You know this natural cycles that align with um, with the moon and, and it's not just humans as well with things like coral spawning that's um, very much tied to lunar phases. Uh and some of that's not very well understood. Uh, but uh, I think the thrust of, of John's question is why, why aren't we being stretched and shrunk like the oceans are? Uh, perhaps I've got it wrong. But anyway that's the answer. Um, and I agree.

sorts of interruptions? Um, I know sometimes uh, there are time sensitive observations of uh, like transits or something um, that astronomers use to determine shapes of ah, objects and stuff like that that uh, need to occur at a specific time. So I was thinking maybe those are something that wouldn't be interrupted. Um, but yeah, that's my question. Thanks, loving the show.

going to last for a very short time. And that happens a lot. Um, the, the, perhaps the best known of those was back in 1987 which I remember very well when that was the last time a naked eye supernova uh, went off in our skies down here in the southern hemisphere. It was in the Large Magellanic Cloud, our nearest uh, dwarf large dwarf galaxy. Uh, it was visible to the unaided eye first for 400 years. Uh and of course the Telescope, our telescope was only 10

years old then. It was state of the art and pretty well everything was pushed off for observations of this, of this object. Um, but um, it is usually um, you know, it's not usually uh, an event, uh, where there will be a conflict between the scheduled observer and the person who was requiring the target of opportunity

observations. It's uh, usually the scheduled observer would have uh, uh, had an understanding at the outset that uh, they might need to stand by and um, let somebody else take over the telescope for the purpose of whatever their observations are. However, uh, Ben's absolutely right. There are some observations which are scheduled which themselves are time critical. And so you would rule out the telescope being taken over

uh, for those events. Uh, one I was involved with, um, because I was astronomer in charge of the telescope at the time. And this is probably 10 years ago there was an occultation of Pluto. Um, so what that means is uh, actually it was an occultation of a star by Pluto. What that means is Pluto passed in front of a distant star, uh, and we could observe the brightness of the star. And what we wanted to do was look uh, at the way the star's light um, diminished uh, as

it passed through Pluto's atmosphere. This actually it was before um, New Horizons flew by Pluto in 2015. So we didn't really know much about Pluto's atmosphere. It's very thin, very tenuous. But the observations that were made actually allowed us to um, you know, form details of it. In particular that it's quite layered. It's not a smooth, smoothly changing distribution. So that was very much a time

critical observation. And you would not get uh, even if there'd been a bright supernova uh, in the sky that night, it probably would not have taken over the telescope. I think it would have, uh, the occultation by uh, Pluto would have been, would have been the thing. And as uh, exactly as Ben says, occultations are when an object passes in front of a star usually or another object. Uh, but it's a way of allowing us to work out the shapes of asteroids and things of that

sort if they pass in front of a star. So that's really quite, quite important observations and very much time critical in themselves. So you wouldn't want them to be taken over by others. But it's a great question.

we keep seeing them annually. If meteor showers such as Persidius occur when the Earth passes through the debris left behind by comets as they orbit the sun, what prevents the Earth from clearing the debris from our orbital path after the first pass, leaving our orbit free of debris until the next comet pass, uh, uh, next comet comes past. Cheers Dave. And then we have Brian with his question which is similar. And then Brian says, can you explain the orbital dynamics associated with annual

meteor showers? We orbit the sun, but the whole solar system is rotating around the Milky Way, which itself is moving. So is the comet trail in a static stripe of debris which we bisect on the same point in our orbit total in our orbit each year or is it in the orbit of the sun or a galactic center or other? If it's in our solar orbit, why do we catch up with it? And why don't we effectively leave a hole in the debris diminishing the meteors every year from the dark state, uh, from the dark

stars. North Yorkshire Moons National Park. Professor Fred Watson: Yeah, the national, It's North Yorkshire, um, Moors National Park. It's a place I know well in fact, uh, in the north of England and they do have dark sky, dark stars. Uh, this is from Brian there. I wonder whether Brian knows my friend Paul Cass who also works at the North Yorkshire Moors Dark Sky Park. Anyway, that's a different uh, aspect of all this Heidi. Um, and I might mention that um, they've uh. Dave who had.

The other question was from, from Inverell here in New South Wales. So a question from the UK and a question from Australia, both effectively asking the same thing which I thought was uh, worth while bringing these two people together. So yes, the, the bottom line is, and you've got to sort of think of it in three dimensions, um, it is to do with the orbits of comets. Uh, a uh, comet moves in a usually a very elongated

orbit. Um, and the sun is um, one end of um, uh, passes close to the sun and then disappears into the depths of the solar system. Uh, when it gets near the sun, uh, the comet starts basically projecting dust, uh, and that dust trail remains within the comet's orbit. And so those dust particles are sort of moving with the comet. They're um, moving in the orbit as well. But they smear out because they've got

their own uh, motion. And so essentially ah, a comet leaves a trail of dust exactly in its orbit and if that orbit intersects the Earth's orbit, then the Earth will pass through the trail of dust. And that's exactly what it does. And when that happens, that's when we get a meteor shower. But the reason why, um, you know, it doesn't soak up all the dust as it goes through is because that dust itself is moving. Uh, and, um, it's not just a single dust cloud that you're

punching a hole in. The dust is a stream of stuff that's moving through space with the same velocity, more or less as the comet had. Uh, and so what you've got is a region of space that's rich in dust, but it's being replenished, um, by the motion of the particles. So, yes, the Earth plows through, uh, doesn't really make a hole in it because, you know, we only sweep up, um, 12,000 km diameter worth of it, because that's the Earth's

diameter. Um, and the dust stream might be many, uh, tens of thousands and perhaps even millions of kilometers, uh, wide. Maybe not millions, but certainly tens, hundreds of thousands, possibly. So you've got a wide trail of dust that is a reservoir for the Earth to sweep up and see the meteor showers. So it's constantly being replenish. That's the bottom line. Uh, and hopefully that's the answer to both those gentlemen's questions.

All right, so our last question is. Excuse me. An audio question from Lou.

again, a place I know well. I grew up not very far from Manchester in the north of England. So this has been a bit of, a, bit of a nostalgia segment for me. Um, but the great question, uh, you know, is the, is the Goldilocks Zone applicable to all extraterrestrial life? And I think the answer is no. Uh, because we, when we talk about the Goldilocks Zone, it's that region surrounding a star where the temperature is not too hot and it's not too cold, but it's just right for, for life

to exist. It's why it's called the Goldilocks Zone. I've got a feeling it was a colleague of mine who coined that expression as well. A long, long, um, uh, it relies on the fact that we are, ah, beings. In fact, all life on Earth is uh, based uh, on water. We use water as our working fluid. Uh, as you mentioned, um, in our question on tides, Heidi, most of our bodies are made of water. Uh, and the same is true of most living organisms. Uh, water

is a large part of it. And so liquid, uh, water is for us, uh, the, perhaps the strongest feature that um, might be used as an indicator of where life might form. If you've got water, maybe you will have life. That's always been the mantra. Follow the water. Um, so the Goldilocks Zone is where you could put a planet and it would be capable of having liquid water on its surface. Not frozen, not vapor, but liquid, which is what we need.

So it's very specific is the Goldilocks Zone to um, life forms that are like ourselves, that are based on water and. Yeah, well, maybe if there is life anywhere else in the universe, it will be based on water. But there are other possibilities as well. And people have wondered whether perhaps the season lakes of Titan,

one of Saturn's moons, uh, whether. Which are made of liquid ethane and methane, whether they might have, uh, living creatures in them that rely on those supercooled liquids as their working fluid. We don't know. We've not seen any evidence of that. But it is possible. And so if that was the case, then you'd be looking at entirely different type of Goldilocks Zone. If liquid natural gas was what you needed, uh, for these creatures, uh, then your Goldilocks Zone will be a very different one

from the one that we have. It will be much further from your parent star. Uh, so Goldilocks Zones are not universal. They're not, um, kind uh, of, you know, common to all species because we don't know enough about what other species might be like. But it's a good start. That's why we look at the Goldilocks Zone with interest because the only life forms that we know use water. Uh, and Goldilocks Zone is where water might exist. So that's why we look there.

up with four hypothetical planets. One of them's a jungle, one of them's a desert. One of them is, um, the atmosphere is so dense that it's almost like water. So there's all these animals that look marine like, but they are like birds. And it's very cool just to play around because they use real physics and then talk about the hypothetics. It's kind of fun. Then I won't tell you about the last planet, because it's kind of a. It's a fun surprise. It's a fun surprise planet. It's not Earth.

It's not Earth. Um, it's a very interesting hypothetical planet. Um, but I do recommend that show. Professor Fred Watson: Sounds great. I'll check it out. Sounds, Heidi. Yeah, it's a good one. Um, well, I guess that's it for our Q and A episode. So I just want to say, if this is my last episode, that it has been an absolute pleasure and delight being on here. Thank you all for your wonderful and kind questions. Fred, thank you for having me. If y' all want to stay in touch, you can follow

me on LinkedIn. My. It's just my name, Heidi Campo, which is C, A, M, M, P, O. And then I think it's on. There is comma, C S, C S, which is one of my certifications. That would be Comet sun, if we're spelling it phonetically. Comet son. Comet son. So, Heidi Campos, C.S.C.S. if you want to follow me on LinkedIn, I'm also on Instagram, but it's mostly just pictures of my dog and me talking about fitness stuff, which may not be everybody's cup of tea. Um, Fred, it's been a delight. Thank you.

Professor Fred Watson: Oh, it's been a delight for me too, Heidi. And, um, I hope we do this again sometime. It might be next week, but. It might be next week. It might be next week. Yeah, we'll be in touch. And I'm. I'm always here if you need me. Um, till then, we'll catch, uh, you all next time. Professor Fred Watson: Take care.